Conventionally, there has been known a solid oxide fuel cell stack in which fuel cells and interconnector plates are alternately stacked to form the fuel cell stack. Each of the fuel cells includes, for example, a flat plate-shaped solid oxide layer (a solid electrolyte layer), an anode disposed on one side of the solid oxide layer and in contact with fuel gas, a cathode disposed on the other side and in contact with oxidant gas, and passages (a fuel passage and an air passage) reaching the anode and the cathode.
Specifically, one known fuel cell used as the above-described fuel cell includes, for example, a single cell including a solid oxide layer with an anode and a cathode provided thereon; a separator joined to the solid oxide layer to separate the fuel gas passage and the oxidant gas passage from each other; an anode frame disposed around the anode; a cathode frame disposed around the cathode; and an interconnector disposed on an outer side of the fuel cell with respect to its thickness direction.
In one known fuel cell stack, manifolds for the fuel gas and manifolds for the air are provided in outer edge portions (frame portions) of the fuel cell stack so as to penetrate the fuel cell stack in its stacking direction, in order to supply the fuel gas and the air to the fuel passages and air passages of the stacked fuel cells and to discharge the (reacted) fuel gas and the air from the fuel passages and air passages of the fuel cells.
In a technique recently developed, each frame-shaped seal member is disposed between adjacent components of a fuel cell stack (e.g., between an interconnector and a separator) so as to surround the outer edge portion of the corresponding single cell and to surround manifolds, in order to prevent gas (particularly, fuel gas) from leaking from, for example, gaps between the stacked single cells of the fuel cell stack.
Techniques proposed to provide gas sealing using such seal members as described above include: a technique that uses compression seal members (which provide sealing under application of pressure) formed of, for example, mica (see Patent Document 1); techniques that use seal members containing glass or glass ceramic (Patent Documents 2 and 3); and a technique that uses ceramic seal members concentrically surrounding manifolds (see Patent Document 4).